December. 1921. 



SCIENTIFIC AGRICULTURE 



125 



Variation and Inheritance in Red Clover 



M. O. MALTE Ph. D. 



Dominion AoTostolonfist, Central Experimontal Farm, Ottawa. 



(Continued from last issue.) 



II.— INDIVIDUAL VARIATION AND 

 INHERITANCE OF CHARACTERS. 



The Marking's of the Leaves. 



. . Causes and occurrence of the markings. 



— Great variations occur, as is Avell known, 

 in respect to the markings of the leaves. 

 Most red clover plants have the leaflets 

 marked with a white olotch which, ac- 

 cording to Kajanus (2, p. 40), is being 

 formed in the following way: The flat- 

 tish epirdermis cells of the upper leaf sur- 

 face multiph' in certain areas at a faster 

 rate than do the palisade cells under- 

 neath, the result being that spaces filled 

 with air are created between the latter 

 cells. At the same time the lower walls of 

 the epidermis cells bulge out, giving the 

 cells in question the shape of plano-con- 

 vex lenses. As a consequence the palis- 

 ade cells located underneath are being 

 exposed to more intense light which, in 

 turn, brings about a partial destruction 

 of their chlorophyll. The markings of 

 the red clover leaves are consequently 

 caused by the presence of air-fille_d spaces 

 between tjiie palisade cells combined with 

 a partial destruction of the chlorophyll in 

 the said cells." 



The white or whitish markings are gen- 

 erally located at or around the central 

 part of the leaflets. In some plants hoM^- 

 ever, they may be found towards the 

 apex of the leaflets and, in others, al- 

 though rarely, at the very base. While 

 generally V-shaped, the markings have 

 in many types the form of a small triangle 

 or even almost a circle. 



In some types the markings are very 

 obscure and in others they are absent al- 

 together. The absence of markings has, 

 by the w^ay, sometimes been used to de- 

 fine certain commercial varieties. Thus, 

 the English Cow-grass or Mammoth clover 

 is generally said to lack the markings and 

 as a consequence to be characterized by 

 pure green leaves. This is, however, only 

 approximatelj' correct, as the Mammoth 



clover, or at least what is sold as Mam- 

 moth clover, generally seems to contain a 

 large number of forms marked in the or- 

 dinary fashion. As, on the other hand, 

 plants lacking the white markings are 

 practically always found in any "var- 

 iety" of Red clover, it is apparent that the 

 presence or absence of leaf markings can- 

 not be used as a reliable variety char- 

 acter (efr. Clark & Malte 1, p. 105). 

 Hereditary Inheritance of the Leaf Mark- 

 ings. — Concerning the hereditary charac- 

 ter of the leaf markings, some interesting 

 investigations have been conducted by 

 Kajanus and Gmelin. 



Kajanus (2. p. 39) distinguishes between 

 central markings, i.e., markings occurring 

 at or about the centre of the leaflets, and 

 basal markings, i.e., markings occurring at 

 the base of the leaflets. In respect to the 

 former Kajanus (2. p. 41) found, when 

 studying the progeny of open-fertilized 

 plants, that some of the plants display- 

 ed undoubted Mendelian segregation. Six 

 plants gave the following progenj^ : 

 No. of Plants with 

 mother central Without 

 plants. markings, markings. Total. 



Kajanus concludes from this table, in 

 the first place, that, as plants with, and 

 without markings were obtained at the 

 ratio of about 3:1, segregation takes place 

 in accordance with the mono-hybrid for- 

 mula and, secondly, that the presence of 

 leaf markings is dominant over its ab- 

 sence. The recessive character of the 

 lack of markings was further substan- 

 tiated by the fact that plants having no 

 markings whatever gave, when open- 

 fertilized, progenies showing an over- 



